Tires play a critical role in the safety of drivers and passengers. According to the Oregon State Police, “tires are the single most important mechanical component of vehicle control and safe driving.” As the only part of the vehicle in contact with the road surface, tires must provide traction and stability under diverse driving conditions. Further, the tires must provide traction and stability for various types of vehicles.
The behavior of tires on wet or snowy surfaces is of considerable interest from a safety point of view since many accidents occur on slippery roads. It is known that tire performance can be impacted by vehicular speed, surface texture and depth of precipitation on the road. However, it is a tire's tread pattern, tread depth, tread material, air pressure and intended use that has the most impact on performance in adverse conditions.
The effects of tread pattern and tread wear on wet surfaces have been studied experimentally by a number of investigators, and have been shown to play a significant role in road adhesion on common road surfaces and in various weather conditions. Generally, tires with more ribs and sipes perform better than those with fewer, and tires with more remaining tread perform better than those with less. Excessively warn, smooth, or close patterned tires do not provide the escape paths for water making hydroplaning more likely in wet conditions and do not provide adequate channels for grabbing and evacuating snow in winter conditions.
Materials used in the manufacture of tires also play a significant role in tire performance in wet conditions. Tires designed for longer life typically use more natural rubber as the base polymer for the tread compound. Tires designed for improved rolling resistance, and performance typically use more synthetic rubber as the base compound for tread design. The natural rubber compounds offer higher abrasion resistance, synthetic rubber compounds offer a higher value of coefficient of road adhesion, particularly on wet pavements. Typically commercial truck tires will be designed for durability and long life, while many passenger car tires are designed for better performance. Performance, however, is always important regardless of the use.
Today tire manufacturers have the technology and capability to design and manufacture tires with specific functions in mind. Today's market is filled with “All Season”, “Off the Road”, “Light Truck”, “Performance”, “Comfort”, “Winter”, “Run Flat”, and “Commercial” tires. Within each market segment, engineers develop tread designs and use specific materials for an intended outcome. “Performance” tires will use a specific tread design and material base to improve traction, while a “Commercial” truck tire will be designed for durability and longevity for highway driving. In some instances, tires are designed with multiple functions. For example, the shoulder regions are designed for summer traction with deep channels to evacuate water while the middle rib is made of a highly siped, low durometer rib for winter traction on ice and snow. Tires do not perform equally in common conditions, yet safety and performance concerns remain consistent.
As important as tires are to transportation safety basic maintenance, performance and replacement issues are easily overlooked. Tires worn to the point at which expected performance drastically declines, is irregular, or excessive for any driving condition need to be identified.
Today's modern vehicle is complex and difficult for an individual to maintain independently. Individuals changing their own oil, or spark plugs is a thing of the past. Tire maintenance, however, is still the responsibility of the vehicle owner. Currently, there are three methods available for evaluating a tires remaining tread depth: (1) tread depth gauge or penny, (2) wear bars and (3) evaluation by a mechanic or tire dealer.
To measure tread depth with a tread depth gauge, the user inserts a probe into a groove and pushes a flange on the device flush against the tread. The depth of the tread is then read from a calibrated plunger or dial. To measure tread depth with a penny, the user inserts a penny into a groove with Lincoln's head in the groove. If part of Lincoln's head is always covered by the tread, there is more than 2/32″ of tread depth remaining.
Wear bars are narrow bands of rubber in the grooves across the tire tread that indicate when tires are worn out. They are built in to every tire and will show up when only 2/32″ of tire tread remains. If wear bars are visible, new tires are needed as soon as possible.
For those consumers who are unfamiliar with the penny test and unwilling to learn how to use a tread depth gauge, the only other choice is to bring their motor vehicle to a mechanic or a tire dealer for evaluation. Not only is this expensive, the consumer must rely on the honesty of the mechanic or tire dealer. Although the majority of mechanics and tire dealers are honest, they have a significant financial incentive to encourage the consumer to replace tires that may still have valuable tread.
While the above tools may be effective for someone who understands how and when to use them, they have been shown to be ineffective for most of the marketplace. Industry and government efforts to educate the public on tire safety, including monthly checks of tire pressure and tire tread, are extensive. Yet, over half of all drivers cannot identify a wear bar,1 two out of three drivers do not know how to judge when a tire is bald,2 and nine percent of vehicles on the road today have at least one bald tire.3 1 RMA Survey, February 2002 (FrederickPolls).2 RMA Tire Safety Fact Sheet 20043 Department of Transportation HS 809 359, October 2001
Therefore, it would be desirable to have a tire with continuously visually obvious tread wear indicators that visually identifies various stages of wear, demands attention, creates social pressure for action and results in improved traffic safety.